On designing your own continuous supports for custom parts

[Woadism]

Hi all

 

I've been working, for a painfully long time, on making my own 24th scale Piper Tomahawk, in as much detail and as close to regular injection-moulded standards of quality as I can.

One of the issues I've had to tackle is how to deal with parts that warp while they cure - this was particularly evident in an early iteration of the tail, which I had designed in two halves - I guess because that's what's in the majority of off-the-shelf model kits:

 

 

It was also took a long time to generate the supports, because Chitubox's auto support tools aren't up to the task for something like this.

 

I decided to try modelling a frame that would brace the part as it cured, and went through various iterations of that:

 

 

The light-weight ones only stopped the warping where they touched, leaving bulges, and the heavy raft - aside from wasting a lot of resin - was too firmly attached and would break the part itself on removal.

 

Now - my eventual solution for this particular part was to model it in one piece (and my apologies for the state of these photos - advertising copy they are not) - because parts being in two halves is obviously a design consideration for injection moulding that doesn't always apply to 3D printing:

 

 

...but the issue of how to better brace and support parts, and avoid (or at least mitigate) the damage of support removal, remained.

 

Recently, however, I came across some posts by Hugh Evans about his development of continuous supports in an Elegoo Saturn series facebook group: https://www.facebook.com/groups/elegoosaturn - I won't copy his images here, but basically he's custom modelling a fine continuous support along the edge he wants to support rather than relying on the point supports generated by Chitubox or Lychee to direct contact the model.

 

It was also covered / tested out by Uncle Jessie in a recent video: 

 

 

This caught my attention as an approach that might offer some solutions. Modelling a custom continuous support could allow for smooth continuous supporting of edges without the dimpling effect of regular supports, and let me design custom braces as necessary.

 

As a test, I made some custom supports (loosely modelled on the dimensions of the supports I use in Chitubox) for a part I wanted to run a test print of - and although there's room for some fine-tuning, and there wasn't any bracing required for this part, I think it worked really well:

 

 

You can see how little material was required in the light shining through the 2nd photo.

This part has some really fine edges, and some awkward angles. Making custom supports let me spread the support load more evenly, avoid the 'pimpling' on the bottom, and even let me support that whole back edge which I couldn't do effectively in the normal tools.

 

Conclusion: if you're modelling your own parts, it might be worth designing your own supports, too - I suspect I'll be doing this throughout the project now.

 

 

 

[TheBaron]

Much appreciate you posting this information as it deals with a problem I'm no stranger to either: I've used a similar process on long thin items like rotor blades.

 

@Serkan Sen on this forum has developed his own strategy to great effect on his own builds as well that are worth seeking out.

[Ebf2k]

Thanks for the tips about supports, but in your OP you state the parts that warp while they cure.  To me that indicates there are issues in the curing process.  How are you curing your parts?  Maybe one side is curing more than the other which is causing it to shrink faster/more and cause the warping.  

[nick]

I do it all the time, it's the only way to go IMHO for stuff like this. You get complete control over scaring to it's much easier to remove a continuous or broken line on a visible surface than a load of pock marks. The printining is more consistent too if you care about repeatability.

 

 

I often break them up a bit as you can see, this works well too.

 

This has got 'sacrificial' surfaces too. Think, conventional resin casting where you have a lump to sand away. This works well for the base of this block. It makes it too substantial to warp and you get a perfectly flat, out of sight mating surface after sanding.

 

Nick

[Smnmsn]

I always thought I should do something like this, but having never seen it around, I thought it was just a stupid idea. I'm happy someone made this; did you follow a tutorial or something?

Edited October 17, 2023 by Smnmsn

[nick]

4 hours ago, Smnmsn said:

I always thought I should do something like this, but having never seen it around, I thought it was just a stupid idea. I'm happy someone made this; did you follow a tutorial or something?

No tutorial I just made it up as I went along based on what I wanted it to do. 

[Smnmsn]

Can I ask you the thickness used and if it was difficult to remove?

[Woadism]

On 8/23/2023 at 2:58 AM, Ebf2k said:

Thanks for the tips about supports, but in your OP you state the parts that warp while they cure.  To me that indicates there are issues in the curing process.  How are you curing your parts?  Maybe one side is curing more than the other which is causing it to shrink faster/more and cause the warping.  

 

I had been using either sunlight or a home-made station in a large shiny metal cooking pot wound around the inside surface in a spiral with a long length of UV LED string light. Your comment stuck in the back of my brain and I finally got a proper curing station (the Elegoo Mercury) and man, it really is night and day. This thing is so much better than my terrible DIY attempt. Lesson learned - it has almost completely solved warping issues I was experiencing and is far quicker too - thanks for leading me here (eventually).

[Ebf2k]

Awesome!  Glad you got it sorted!